In acetic acid fermentation, it is known that proliferative capacity and fermentative capacity of acetic acid bacteria decrease as fermentation proceeds. The decrease in the fermentative capacity of an acetic acid bacterium along with the increase in acetic acid concentration in a culture solution is particularly significant in the production of high-acidity vinegars mainly used for industrial purposes. Therefore, improvement in culturing method and acetic acid bacterium used have been attempted in order to increase fermentation efficiency and the achievement level of acidity (acetic acid concentration) in a production of high-acidity vinegars.
For example, Patent Literature 1 discloses a method for producing an ultrahigh-acidity vinegar characterized in the gradually decrease of the fermentation temperature. In addition, Patent Literature 2 discloses a method for breeding an acetic acid bacterial strain with improved acetic acid tolerance.